1.
Diversity, life history, and plant associations (477 total species)

The total number of bee species in New York State is estimated to be 477 species in 47 genera. We compiled this list from Mitchell (1960, 1962), which provides a comprehensive guide to the bees of the eastern United States. We included in the list species reported to occur in New York State, as well as species listed from nearby states, such as Connecticut, New Jersey, Massachusetts, Pennsylvania, and Maine. Those species from other states are indicated in the list with a state abbreviation. We have also modified this list to include bee species discovered in or introduced to New York State after 1960 and based on our own collecting experiences, primarily in the vicinity of Ithaca. John Ascher also provided us with his carefully compiled list of the bees of Tompkins County. The complete list is available from the following page: List of New York State Bees. This list includes all described species that we estimate to be present in New York. It should be emphasized that the list may not include all species that occur in New York State because no state-wide survey has ever been conducted. Furthermore, new species of insects are discovered at a rapid rate, even in areas of the world with well-known faunas, and new or previously undescribed species of bees undoubtedly occur in New York.

Photo
of Hylaeus sp.

As the list indicates, we have 6 of the 7 bee families in New York State (the only bee family not in New York State is the Stenotritidae, a family restricted to Australia), 10 of the 20 currently recognized bee subfamilies, and 47 of the 425 genera in the world. The bees of New York State could best be described as typical of a temperate, Northern Hemisphere bee fauna. In fact, in terms of genera, the bees in the northern parts of the United States (including New York State) are not unlike the bee fauna of Western Europe. Our most common (and speciose) genera are Andrena (112 spp.), Lasioglossum (68 spp.), Nomada (54 spp.), Sphecodes (26 spp.), Megachile (21 spp.), Colletes (20 spp.), Osmia (19 spp.), Hylaeus (16 spp.), Melissodes (14 spp.), Bombus (14 spp.), and Coelioxys (13 spp.). All of these genera are present and common in Europe (Westrich 1989). Much interchange took place between North America and Eurasia across the Bering Land Bridge.

The majority of bees in New York State are digger bees, ground-nesting, solitary bees, such as Andrena, Lasioglossum, and Melissodes. Digger bees comprise roughly 60% of the species of bees in New York State. Species of Andrena are typical of ground-nesting bees in their life history. At the start of the active season (in the spring, summer, or fall, depending on the species) females begin constructing their nests, subterranean systems of tunnels. At the ends of the tunnels, females construct oblong cells which they line with a hydrophobic secretion produced in a gland specifically for this purpose called the Dufour's gland. After foraging on nearby plants for pollen and nectar, they store several loads of pollen and nectar within each cell, form the pollen into a variously shaped loaf or ball, and lay an egg on it. Larvae consume the pollen/nectar provisions. When larvae complete feeding they may enter diapause (a resting stage) as last instar larvae (the developmental stage just before pupation). Most digger bees overwinter as last instar larvae. Development is completed in the following spring or summer, and adults of a new generation begin the cycle again. Some digger bees (such as Andrena, Halictus, and Lasioglossum) overwinter as adults. This is presumed to allow for the earlier adult emergence in the spring.

Other important genera of ground-nesting bees in New York State include Colletes, Halictus, [mentioned above, as digger bee genus] Svastra, and Anthophora. All of these make subterranean burrows, like Andrena. Colletes inaequalis is a common vernal bee in the earliest days of spring. Females construct nests in grassy areas such as lawns, cemeteries, and gardens. Nesting aggregations can be huge (with several thousand nests) and dense (with over 100 nests in a square meter). If you are lucky enough to find these bees nesting in your yard, don't try to kill them; they won't sting, and they are probably good for soil aeration. They are also fun to watch!

Photo
of Megachile sp.

While the majority of bees in New York State are ground nesting, several species also make nests in pre-existing cavities, such as twigs, hollow stems, beetle burrows, or in sites above ground. Many of these bees are mason bees that collect mud, resin, pebbles or other materials to line or construct their nests. Mason bees in New York State include genera such as Osmia, Hoplitis, Prochelostoma, and Heriades. Mason bees comprise roughly 7% of the species of bees in New York State. Other cavity and stem nesting bees include the leaf-cutter bees in the genus Megachile, as well as the yellow-faced bees in the genus Hylaeus. Megachile females line their cells with circular pieces of leaf that they cut from rose bushes and other plants. Hylaeus females line their burrows (constructed in plant stems or other hollow tubes) with a cellophane-like secretion they produce in their Dufour' s glands. Hylaeus are unusual bees because they carry pollen internally and not externally, as do most pollen-collecting bees. Hylaeus is a large genus worldwide, but their greatest diversity is in Australia, where these bees are presumed to have originated.

Another important group of bees are the carpenter bees. In North America we have both small (Ceratina) and large (Xylocopa) carpenter bees. These bees construct nests in wood or preexisting cavities. Xylocopa virginica is a common bee in New York State. Nests are conspicuous because males hover in front of the nests (typically located in fence posts, wooden park benches, and houses) and engage in aggressive territorial battles.

Another important group of bees in New York State are the cleptoparasitic bees. The two largest genera of parasitic bees in New York are Sphecodes and Nomada. Parasitic bees comprise roughly 25% of the bee species in New York State. Parasitic bees are fascinating creatures. They have lost the morphological structures associated with nest construction and pollen collection in most other bees. Instead of constructing and provisioning their own nest cells, parasitic bees enter the nests of other bees (usually when the host female is away) and lay their eggs within the host nest. Once the host female has laid her egg and closed the cell, the parasitic larva hatches from its own egg and kills either the host egg or young larva, then feeds on the host's pollen. Parasitic bees have devious methods for hiding their eggs from the host females. For example, Nomada and relatives (in the subfamily Nomadinae) put their eggs in the cell wall of the host bee's nest. Parasitic bees also have rather narrow host preferences. Nomada, for example, primarily parasitizes nests of Andrena, Epeolus parasitize Colletes, Coelioxys parasitize Megachile, and Sphecodes tend to parasitize other halictine bees as well as some andrenid bees. Remarkably, little is known about the behavior of Sphecodes females when they enter the host nest. Observations on the behavior of Sphecodes would be very exciting.

So far, the vast majority of bees we have mentioned are solitary (or parasitic). Important eusocial bees in New York State include both advanced eusocial taxa in which queens and workers are morphologically distinct (such as Apis mellifera, the introduced honey bee) and primitively eusocial taxa, in which queens and workers are distinguishable from each other only based on size or behavior. Important primitively eusocial taxa include Bombus (bumble-bees; Apidae), as well as Augochlorella, Halictus, and some species of Lasioglossum (Halictidae). We estimate that approximately 18% of the bee species in New York State are eusocial.

While many of the bees in New York State are generalist bees visiting many different plants for pollen and nectar, some species have very narrow host-plant preferences. These specialist bees are referred to as oligolectic. Approximately 20% of the species in the northern portions of the United States restrict their pollen collecting to just a few closely related plant species. For example, many species of Colletes are restricted to plants in the family Compositae, such as Heterotheca, Aster, and Solidago.

Within Andrena there are many oligolectic species. Important host plants for Andrena species include composites, Salix, Cornus, Claytonia, Rhus, Malus and Prunus. Native bees that visit apple trees in the spring are undoubtedly contributing to the greater than $100-million apple industry in New York.

Among the more interesting and economically important bees in New York State is Peponapis pruinosa, an oligolectic bee on Cucurbita (Cucurbitaceae; squashes, gourds, and pumpkins). Pumpkin growers are well aware of the importance of this bee for pumpkin pollination, and many are knowledgeable about the nest site requirement of P. pruinosa.

Genera of long-horned bees (Eucerini) related to Peponapis include Melissodes and Svastra. These genera include species that are primarily restricted to plants in the family Compositae. Among the halictid bees, there are a small number of specialist species. Lasioglossum (Sphecodogastra) oenotherae is an oligolectic bee visiting cultivated Oenothera (evening primrose) in the early morning hours. Dufoureae novaeangliae is another oligolectic halictid bee with a close association with plants in the genus Pontederia (Pontederiaceae).

Bees in the genus Macropis (Melittidae) are oligolectic on Lysimachia (Primulaceae). Members of this genus are oil-collecting bees that use floral oils for both cell lining and larval provisions. Melittid bees comprise a tiny proportion of the bees in New York State. Their greatest diversity is in southern Africa.

2.
Introduced beesThere are known to be a total of 22 introduced bees in North America, many of which occur in New York State (Ascher 2001, Cane in press). All of the known introduced bees have been transported from the Old World (Eurasia) either accidentally or through intentional introduction. The most common and conspicuous of our introduced European bees is the honey bee, Apis mellifera, which is managed commercially for honey and pollination services. Other introduced bees include species of Megachile, Hylaeus, Chelostoma, Hoplitis, Anthidium, and Andrena (Ascher 2001). Ascher estimates that accidentally introduced bees account for 0.5% of the North American bee species. In the vicinity of Tompkins County, 5.2% of the species are accidentally introduced. While they comprise a small number of species, introduced bees make up in some cases a large proportion of the individuals in New York State. This is especially true of the European honey bee. Most accidentally introduced bees are stem- or cavity-nesting species. These species (in the Hylaeinae, Megachilidae, and Xylocopinae) are easily transported in plant materials (e.g., wood) or in man-made materials.

We do not know what effects (if any) introduced bees have had on the native bee fauna of New York State. European honey bees undoubtedly compete with native bees for pollen and nectar and may have caused declines or extinction of some native bees. However, in spite of much research on the topic, it is difficult to disentangle the role of honey bees from the direct effects of human-mediated changes in habitats (Huryn, 1997).

Karen Goodell (Rutgers University) has several papers in press on the impacts of honey bees on native bees in New York (specifically on Long Island). Her study demonstrates that honey bees adversely affect native bees in two ways. First, they compete with native bees for pollen and nectar, which results in lower reproductive output for native solitary bees. Second, the presence of honey bees is associated with higher parasitism rates in native bees, thus leading to lower reproductive success of native bees (Karen Goodell, pers. comm.). Much more work could be done on the interactions between native and introduced bees.